Cathytoo,
We have friends that train national champion protection dogs, police dogs, drug, etc along with training problem dogs. I asked them about this case and they said it is likely not to be a physical problem though it is always good to rule that out. They also said that before you drug the dog take the dog to a really good trainer. In thier experience, dogs that behave that way generally do so out of "Fear aggression". They also indicated that, if the owner is educated and willing to work with the dog, the success rate is usually above 90%. They said that you will need to understand the breed characteristics, pack behaviour, what environmental inputs mean to the dog and how to correct the behaviour. Generally if you understand pack dynamics and what pushes your dog to do this, you can resolve the problem without drugs.

Just a thought.....
Mark